Household appliance lights are well known in the art in many embodiments. The household appliance lights are typically used for illuminating an interior space of a household appliance during operation or for a user to look into the interior space.
No matter whether the household appliances are used for storing food products, for example cooling devices, or household appliances for cooking food products, for example ovens, there are particular requirements which are typically contradictory and hard to meet in their entirety. As matter of principle the illumination of the household appliance interior shall facilitate a sufficient visual perception of the food products by the user which often causes shading problems for example from inserted floors in refrigerators or baking sheets in ovens. Furthermore the illumination shall not blind the user wherein technical components that prevent the blinding cause detrimental light losses.
Using LED's as illuminants has led to new options in the illumination of household appliances. By the same token this technology generates new challenges for engineers.
In particular for cooking devices for food products for example ovens or steam cookers considerable design efforts have to be made in order to prevent an overheating of the LEDs and associated damages. For this purpose not only the heat generated by the LED's have to be removed. Furthermore measures have to be taken in order to minimize temperature loads imparted upon the LEDs by the cooking process.
DE 10 2009 002 775 A1 shall be used as an embodiment for a cooking device light that is known in the art. The light is supported in a known manner in a light housing in a housing cut out. The light exit opening of the light housing is provided with a light permeable cover element which primarily protects the interior space of the light against contamination, but which also already provides a first heat barrier. The light housing includes a cylindrical spacer element at an end that is oriented away from the interior of the cooking device, wherein a cylindrical enveloping surface is enveloped by a reflection material. The circular cover surfaces of the cylinder are provided with light permeable cover elements. The cylinder thus configured is used on the one hand side to offset the LED that is arranged at an end of the cylinder that is oriented away from the cooking cavity as far away from the cooking cavity as possible and to minimize the heat load by this first measure. Additionally the cover elements form additional temperature barriers. The cylinder itself is additionally used as a light shaft in order to run the light emitted by the LED in a direction towards the cooking cavity. Eventually the LED is mounted on a cooling element as an additional measure so that a residual of the operating heat which reaches the LED through the heat barriers can be dissipated.
It is furthermore known from non-patent literature to provide a cavity between the LED and the light exit opening of the inner wall of the cooking space with a light permeable insulation material. Thus, the heat radiation originating from the cooking cavity is minimized and the illumination of the interior space is facilitated.
In the known art the described measures for offsetting the LED from the cooking cavity and for heat shielding reduce the light yield and the illumination quality of the interior of the household appliance. In order to compensate for the reduced light yield more powerful LED's can be used, but their higher operating temperature causes problems.
WO 2009 141 068 A1 or EP 15 98 682 A2 use light conductors in order to conduct the light from a portion that is remote from the cooking cavity into the cooking cavity. The ensuing highly directed radiation, however, requires a plurality of light outlet openings and depending on the technical implementation, a plurality of light sources and light conductors. Additionally the plurality of punctiform sources in the inner housing wall with their high level of brightness is perceived as unpleasant so that these solutions are not very popular due to being expensive and due to a lack of comfort.
Eventually for an optimum illumination of the interior of the household appliance, in particular for cooking devices it is advantageous to arrange plural lights in the housing side walls between the levels provided for the support elements. Thus a light is associated with each of the support elements for ovens, for example with each level that is provided for a baking sheet, so that a shading by additional carrier elements does not impair an illumination quality of the respective level.
Due to the standardized outer dimensions and the goal to keep the usable interior of the cooking device as large as possible the installation spaces provided between the lateral interior walls are rather limited. This makes it difficult to design household appliance lights for cooking devices for using LED's since the distance between the cooking space and the LED that can be used for temperature protection is limited.
Thus, the light losses inherent to the known devices cannot easily be compensated by more powerful LED's in particular when the household appliance light is arranged behind a side wall of a cooking cavity since the more powerful LED's typically generate much more waste heat.